The present invention generally relates to cylinder valves, and more particularly to a cylinder valve having a thermal relief device.
Certain specialty gas cylinders require high pressure valves for selectively releasing pressurized gas from the cylinder. Some of these prior valves are made of brass, but when the valves are intended to be used with gases that react with brass, such as hydrogen sulfide, the brass valves are usually plated. For example, some brass valves are nickel-plated to protect the brass from the gas. The plating can become chipped, pitted, or otherwise damaged, allowing a reaction to occur between the gas and underlying brass.
Because the reaction between the gas and brass can alter the concentration and composition of the gas mixture in the cylinder, some conventional valve bodies are made of aluminum. One such conventional valve is designated in its entirety in FIG. 1 by the reference number 10. The valve 10 has an aluminum body 12 and a thermal relief device, generally designated by 14, mounted in a vent passage 16. The thermal relief device 14 includes an insert 20 having a plug 22 made of an alloy (i.e., solder) that melts at a predetermined temperature to allow gas to escape through the vent passage 16 should temperatures of the valve 10 or gas become too high. Because the solder does not easily or readily adhere to aluminum, the insert 20 is made of nickel-plated brass. The insert 20 presents a much smaller plated area that is exposed to the pressurized gas than a valve having a nickel-plated body. Further, the insert 20 is recessed in the body 12. Thus, the insert 20 has less opportunity to become damaged and to react with gas. One example of the aluminum valve is described in U.S. Pat. No. 8,327,868, which issued on Dec. 11, 2012, and is assigned to Control Devices, LLC, a Delaware corporation having a place of business in St. Louis, Mo.
Still, there is a need for an improved cylinder valve having a thermal relief device that does not include brass to entirely eliminate the potential for a reaction to occur between the valve and gas in the cylinder.